TD LTE secondary component carrier in unlicensed bands

ABSTRACT

A method is provided for communication in a wireless telecommunication system. The method comprises adaptively designating, by a network element following a frame-based communication protocol, for use as a secondary component carrier in a carrier aggregation scheme, at least a portion of radio resources on an unlicensed band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/572,092 filed on Aug. 10, 2012 entitled, “TD LTE Secondary ComponentCarrier in Unlicensed Bands”, which is incorporated by reference hereinas if reproduced in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to component carriers in wirelesstelecommunications systems.

BACKGROUND

As used herein, the term “user equipment” (alternatively “UE”) might insome cases refer to mobile devices such as mobile telephones, personaldigital assistants, handheld or laptop computers, and similar devicesthat have telecommunications capabilities. Such a UE might include adevice and its associated removable memory module, such as but notlimited to a Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. Alternatively, such a UE might include the deviceitself without such a module. In other cases, the term “UE” might referto devices that have similar capabilities but that are nottransportable, such as desktop computers, set-top boxes, or networkappliances. The term “UE” can also refer to any hardware or softwarecomponent that can terminate a communication session for a user. Also,the terms “user equipment,” “UE,” “user agent,” “UA,” “user device,”“mobile device”, and “device” might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an Evolved Universal Terrestrial Radio Access Network(E-UTRAN) node B (eNB), a wireless access point, or a similar componentrather than a traditional base station. Any such component will bereferred to herein as an eNB, but it should be understood that such acomponent is not necessarily an eNB. Such a component may also bereferred to herein as an access node.

An eNB or similar component that has a small coverage area such as ahome may be referred to as a home eNB (HeNB) or a femtocell. Thediscussion hereinafter may focus on HeNBs, but it should be understoodthat the embodiments disclosed herein are not necessarily restricted toHeNBs. An access point compliant with the IEEE 802.11 standards may bereferred to as a WiFi access point (AP). LTE, WiFi, and othertechnologies that may be used in wireless communications may be referredto as radio access technologies (RATs).

LTE may be said to correspond to Third Generation Partnership Project(3GPP) Release 8 (Rel-8 or R8) and Release 9 (Rel-9 or R9), and possiblyalso to releases beyond Release 9, while LTE Advanced (LTE-A) may besaid to correspond to Release 10 (Rel-10 or R10) and possibly also toRelease 11 (Rel-11 or R11) and other releases beyond Release 10. As usedherein, the terms “legacy”, “legacy UE”, and the like might refer tosignals, UEs, and/or other entities that comply with LTE Release 10and/or earlier releases but do not fully comply with releases later thanRelease 10. The terms “advanced”, “advanced UE”, and the like mightrefer to signals, UEs, and/or other entities that comply with LTERelease 11 and/or later releases. While the discussion herein deals withLTE systems, the concepts are equally applicable to other wirelesssystems as well.

In an LTE system, uplink (UL) and downlink (DL) transmissions areorganized into one of two duplex modes, frequency division duplex (FDD)mode and time division duplex (TDD) mode. The FDD mode uses pairedspectrum where the frequency domain is used to separate the UL and DLtransmissions. In TDD systems, on the other hand, unpaired spectrum isused where both UL and DL are transmitted over the same carrierfrequency. The UL and DL are separated in the time domain.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram of LTE femtocells and WiFi access points.

FIG. 2 depicts the coexistence of different radio access technologies onthe same carrier frequency.

FIG. 3 is a diagram of IEEE 802.11 distributed coordination functionoperation.

FIG. 4 is a diagram of TD LTE radio frame configurations.

FIG. 5 is a diagram of a primary component carrier in a licensed TDDband and an unlicensed secondary component carrier in an unlicensedband.

FIG. 6a is a diagram of LTE and WiFi transmissions where a WiFi beaconsignal coincides with an LTE coexistence subframe, according to anembodiment of the disclosure.

FIG. 6b is another diagram of LTE and WiFi transmissions where a WiFibeacon signal coincides with an LTE coexistence subframe, according toan embodiment of the disclosure.

FIG. 7 is a diagram of LTE and WiFi transmissions where a WiFi beaconsignal coincides with an LTE uplink subframe, according to an embodimentof the disclosure.

FIG. 8 is a diagram of LTE and WiFi transmissions where a WiFi beaconsignal coincides with an LTE special subframe, according to anembodiment of the disclosure.

FIG. 9 is a diagram of U-SCC and 802.11 transmissions on the samecarrier when the target beacon transmission time is not a multiple of 10milliseconds, according to an embodiment of the disclosure.

FIG. 10 is a diagram of UE WiFi measurement feedback to a HeNB.

FIG. 11 is a diagram of WiFi beacon timing relative to an LTE subframe,according to an embodiment of the disclosure.

FIG. 12 is a diagram of a portion of the medium access control layer,according to an embodiment of the disclosure.

FIG. 13 is a flowchart illustrating LTE eNB unlicensed channel setup andUE measurements, according to an embodiment of the disclosure.

FIG. 14 is a flow diagram illustrating U-SCC activation, according to anembodiment of the disclosure.

FIG. 15 is a flowchart illustrating an overall coexistence procedurewith respect to HeNB operation, according to an embodiment of thedisclosure.

FIG. 16 is a flowchart illustrating a coexistence procedure for achannel shared with WiFi, according to an embodiment of the disclosure.

FIG. 17 is a flowchart illustrating a coexistence procedure for aconventional licensed TD LTE SCC, according to an embodiment of thedisclosure.

FIG. 18 is a flowchart illustrating a coexistence procedure for a U-SCCwithout WiFi transmissions, according to an embodiment of thedisclosure.

FIG. 19 is a flowchart illustrating a carrier claiming procedure,according to an embodiment of the disclosure.

FIG. 20 is a simplified block diagram of an exemplary network elementaccording to one embodiment.

FIG. 21 is a block diagram with an example user equipment capable ofbeing used with the systems and methods in the embodiments describedherein.

FIG. 22 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents. Embodiments are describedherein in the context of an LTE wireless network or system, but can beadapted for other wireless networks or systems.

An unlicensed band may be considered to be any portion of the radiospectrum whose use is not restricted through a spectrum licensingapproach. In particular, certain bands in the 5 gigahertz (GHz) rangeare known as the Unlicensed National Information Infrastructure (U-NII).Bands covered by the U-NII include U-NII Low (U-NII-1), U-NII Mid(U-NII-2), U-NII Worldwide, and U-NII Upper (U-NII-3). The frequencyrange for U-NII Low is 5.15 to 5.25 GHz. With U-NII Low, the use of anintegrated antenna is required, and power is limited to 50 milliwatts(mW). The frequency range for U-NII Mid is 5.25 to 5.35 GHz. With U-NIIMid, a user-installable antenna is allowed, subject to dynamic frequencyselection (DFS), and power is limited to 250 mW. The frequency range forU-NII Worldwide is 5.47 to 5.725 GHz. With U-NII Worldwide, both outdoorand indoor use are allowed, subject to DFS, and power is limited to 250mW. The frequency range for U-NII Upper is 5.725 to 5.825 GHz. WithU-NII Upper, a user-installable antenna is allowed, and power is limitedto 1 watt.

LTE air interfaces are becoming available in femtocells, which may havea comparable footprint to WiFi access points. Therefore, it may beappropriate to consider leveraging unlicensed bands for LTE operation infemtocell deployments. Such considerations may require an examination ofall aspects of the LTE design to assess the suitability of LTE forunlicensed band use. Time division (TD) LTE may be assumed as apreferred duplexing mode for the unlicensed band, but frequency division(FD) may also be possible.

The introduction of carrier aggregation in LTE may provide anopportunity to use an unlicensed band as a secondary component carrier.By allowing the primary component carrier to carry the bulk of thesignaling and control traffic and other essential licensed band featuresthat cannot be easily replicated for operation in the unlicensed band,the design of LTE in unlicensed bands can be simplified.

It may be necessary to protect LTE transmissions from interference whileLTE coexists with other technologies that are simultaneously in use inthe unlicensed band. Similarly, for coexistence, the LTE transmissionsmay need to consider the interference possibly caused to othertransmissions in the band.

Embodiments disclosed herein provide for a TD LTE transmission operatinga secondary component carrier in an unlicensed band. The embodimentsenable LTE operation to coexist with WiFi in the unlicensed band, asillustrated in FIG. 1. The embodiments enable unlicensed LTE operationwith minor modifications to the TD LTE and carrier aggregation systemdesigns and enable the coexistence of LTE HeNBs and WiFi APs operatingin the unlicensed band without any explicit cooperation between the twosystems.

The embodiments may not directly fit into the Release 10 carrieraggregation (CA) scheme, as described in 3GPP Technical Report (TR)36.808, since use for non-contiguous CA is restricted to selectedlicensed FDD bands and all TDD bands. It may be expected that futurereleases of CA will include unlicensed bands as well. The embodimentsdisclosed herein provide concepts and guidelines for the evolution of CAto include unlicensed spectrum.

In general, two technologies can be called coexisting if they share thesame frequency resources at different times or different frequencyresources at the same time without causing significant interference toeach other. As illustrated in FIG. 2, RAT-b, which is operating on acarrier frequency f_(l1) in a licensed band (over a bandwidth of 2 Δf),may opt to have a second carrier in an unlicensed band if the availablebandwidth is scarce to support the quality of service (QoS) requirementsof the connected and/or incoming UEs and if bandwidth is available in anunlicensed band. In this example, RAT-a is operating in the unlicensedband. RAT-b may operate the carrier f_(u1) as the secondary carrier ifthe resources in the band f_(u1)±Δf are available. However, sometimesall the resources in the band f_(u1)±Δf may not be utilized by RAT-b allthe time, possibly resulting in a waste of resources. Instead, a RAT-c,which is operating on carrier frequency f_(l0), may operate on f_(u0) inthe unlicensed band as a secondary carrier when in need of extrabandwidth. In this case, the same carrier frequency is shared with RAT-ain time. Both RAT-a and RAT-c can coexist on the same carrier frequencybut at different times without affecting their basic functionality.However, it may be desirable for RAT-c to operate such that there is nosignificant degradation in RAT-a's operation. If it is assumed thatRAT-a is not aware of RAT-c, then RAT-c may need to be cognizant of theresource usage and protocol structure of RAT-a. This type of coexistenceis addressed by the embodiments disclosed herein.

In the embodiments disclosed herein, the TD LTE HeNB contains both theLTE air interface and the unlicensed TD LTE (U-TD LTE) air interface,with the former operating in the licensed band and the latter providingthe excess channel bandwidth by leveraging the unlicensed band. Thus,the U-TD LTE may operate only as a secondary component carrier in theunlicensed band (i.e., without the assumption of a database), and mayoperate with centralized scheduling for downlink user data. Sharingaccess with WiFi and other unlicensed users is built into the framestructure.

By way of background information, a brief discussion will now beprovided regarding unlicensed bands, WiFi, and TD LTE. Unlicensed bandsare governed by regulatory restrictions for operation so as to allowcoexistence of multiple technologies using the band. As an example, thetransmit power restrictions for the U-NII Low band require indoor APs tooperate at low power. In addition, Dynamic Frequency Selection (DFS) (inthe radar bands only) and Transmit Power Control (TPC) are mandatory inportions of the band. While the radar band may be avoided, some means ofmeeting the TPC requirements may have to be provided for an LTEtransmission.

The decentralized medium access control (MAC) function utilizing theDistributed Coordination Function (DCF) is shown in FIG. 3 and is themethod that is commonly employed in commercially available APs. DCFoperates in a Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA) mode, thus implementing a back-off procedure prior to datatransmission. MAC Service Data Units (MSDUs) are transmitted followingthe detection of the channel as being idle for a total period (adistributed inter-frame space or DIFS) of 34 microseconds plus a randomtime duration. A request to send (RTS) is optionally initiated by a WiFidevice after waiting a randomly selected time after the channel issensed to be idle for a duration equal to the DIFS. An RTS is notinitiated if the data packet size is below a certain size indicated byRTS Threshold, which is a system-configurable parameter. In a case wherean RTS is not required to be sent, the data packet is transmittedimmediately after the channel is sensed to be idle for a durationindicated by the DIFS. The device transmits the data packet if a clearto send (CTS) frame is received after a time period indicated by shortinter-frame space (SIFS). An acknowledgement is expected to be receivedafter the transmission of the data packet with a delay of SIFS. Typicalvalues of these timers and the frames are defined in FIG. 3. DCF is notrequired in a centralized scheduling setup where at any given instantonly one station is allowed to transmit.

The IEEE 802.11a/n superframe is distinguished by the presence of abeacon frame that is transmitted by the AP at the beginning of thesuperframe and is used for timing synchronization by the stationsattached to the AP. The beacon transmission period is denoted as TargetBeacon Transmission Time (TBTT). The beacon transmission is delayed ifthere is a communication in progress. Only the AP generates beacons inthe Basic Service Set (BSS) configuration comprising an AP and itsconnected stations. Such a configuration is the focus of the embodimentsdisclosed herein, but the embodiments are not limited to such aconfiguration.

DFS is used by the AP to select the frequency channel on which tooperate. This procedure is standardized in IEEE 802.11h for the AP andthe devices. The channel measurement procedure done by the AP is notstandardized. DFS is mandated only for portions of the 5 GHz band whereradar operation is also assigned. TPC is required as an operationalfeature for systems operating in portions of the 5 GHz band.

The physical layer in LTE, being based on orthogonal frequency divisionmultiple access (OFDMA), is similar to the physical layer in WiFi. TheTD LTE Radio frame UL/DL configurations are given in FIG. 4. Asillustrated, a special subframe S 410 is configured within a radio frame420. Based on the UL/DL switching time, there are one or two specialsubframes S 410 within a frame 420. Two different UL/DL switching timesare supported in TD LTE, 10 milliseconds (ms) and 5 ms. The specialsubframe S 410 consists of three fields, Downlink Pilot Time Slot(DwPTS) 430, Guard Period (GP) 440, and Uplink Pilot Time Slot (UpPTS)450. GP 440 includes the switching time from DL to UL. The switchingfrom UL to DL is achieved by appropriate timing advance at the UE. Asshown in FIG. 4, the total length of DwPTS 430, GP 440, and UpPTS 450 is1 ms. However, within the special subframe S 410, the length of eachfield may vary depending on the coexistence requirements with legacy TDDsystems and supported cell sizes. By configuring the subframes 460denoted as “D/U” as either for downlink or uplink, one can obtain sevendifferent UL/DL configurations as tabulated in 3GPP TechnicalSpecification (TS) 36.211. DwPTS 430 is similar to a regular butshortened downlink subframe and contains the reference symbols andcontrol information. In addition, DwPTS 430 includes a primarysynchronization signal (PSS) used for DL synchronization. A secondarysynchronization signal (SSS) is transmitted during the last OFDM symbolof the previous subframe (subframe-0). UpPTS 450 occupies either one ortwo OFDM symbols. A synchronization reference signal (SRS) and a randomaccess channel (RACH) are transmitted by the UE during the UpPTS 450. GP440 can be set to 1-4 OFDM symbols or 9-10 OFDM symbols in length. Thelength of GP 440 is decided based on the cell size.

A limitation that may affect the deployment of LTE in the unlicensedband is that LTE is a frame-based medium access protocol designed forlicensed band use. LTE's MAC frame structure requires that there be asynchronous transmission of the frame. Therefore, a random delay intransmission that is introduced by the CSMA/CA type of contention-basedMAC protocol that is employed in WiFi may not be acceptable. Further,LTE transmissions are managed by the centralized scheduler in the eNBwhile WiFi transmissions rely on MAC procedures such as RTS, CTS and DCFbecause there is no centralized control. These are the major differencesbetween LTE and WiFi in the context of operation in the unlicensed band,where the band may have to be shared with other WiFi users and whereinterference may occur due to other transmissions.

When a secondary component carrier (CC) is operated in the TD LTEconfiguration in 3GPP LTE Release 10, it may be necessary for theprimary CC and the secondary CC to have identical DL/UL configurationsto avoid causing excessive interference at the transceiver.

LTE femtocells are likely to proliferate in enterprise and residentialdeployments. Further, LTE TDD is becoming a mainstream standard as acomplement to LTE FDD. Carrier aggregation has been introduced as afeature in LTE-Advanced and is specifically promoted as being of valuefor dense deployment of small base stations. CA can be applied in thecontext of LTE TDD as well. CA allows a variety of configurationfeatures that support the use of an unlicensed band as a componentcarrier. For example, it is possible to have asymmetric configurations,with an anchor or primary CC (PCC/PCell) having both a downlink and anuplink channel and the additional secondary component carriers(SCC/SCell) configured for only downlink transmission. Thus it ispossible to consider only downlink transmission on an unlicensed bandSCC. Further, different power settings are permitted for the CCs, suchthat an SCC operating in the unlicensed band can be configured to meetthe power level constraints for operation in that band. In addition, thePCC can also carry the majority of the medium access control (MAC)signaling, allowing a substantial simplification of operation of LTE onthe SCC. These features of CA may motivate the consideration of a “lightLTE” transmission in the unlicensed band. Further, since there is oneMAC per user, and link adaptation is performed per CC, the LTE CA designmay make it convenient to incorporate the unlicensed band DL on the SCC.

With this background information in mind, it may be seen that it may belikely for LTE femtocells to coexist with WiFi APs on the same 20megahertz (MHz) channel. Therefore, it may be necessary to consider thecoexistence of U-TD LTE with WiFi. It may also be necessary to considerthe improvements that may be needed for coexistence with a different RATon the same carrier. It may further be necessary to consider the conceptof coexistence in the LTE design for unlicensed operation where, evenwithin the context of a frame-based protocol, the band can be sharedwith other users. Some means of protection of the LTE transmission maybe needed for dealing with the interference that may arise from acoexisting WiFi transmission.

The embodiments disclosed herein provide novel methods for U-TD LTEincluding the case where U-TD LTE and WiFi may coexist on the samecarrier within an unlicensed band. The description herein addresses ascenario where an unlicensed carrier is used to offload downlink trafficfrom TD LTE operating over a licensed carrier. However, it isstraightforward to extend this procedure to offload both the downlinkand uplink traffic onto the unlicensed carrier.

It may be assumed herein that a femto eNB or HeNB is operating over acarrier frequency f_(L) within a licensed band using TD LTE. In the samegeographical area, a WiFi AP is operating over a carrier frequency f_(U)within an unlicensed band. As the demand for bandwidth increases overf_(L), the LTE eNB may offload some of the DL traffic onto theunlicensed carrier f_(U) with minimal or no impact to the 802.11operation on the carrier f_(U). The data traffic to and from the UEsthat are capable of operating over both the licensed and unlicensedbands may be offloaded to the unlicensed carrier. As referred to herein,a UE capable of operating over both the licensed and unlicensed bandsmay be considered to be a UE that is capable of transmitting andreceiving over both the licensed and unlicensed bands and that may alsobe compliant with the modifications specified herein. Legacy UEs maystill be kept on the licensed band.

One way of offloading the traffic is by enabling an SCC on f_(U) anddirecting DL traffic to the SCC. However, since the operation of LTE onthe unlicensed carrier should not cause any significant impact to theexisting WiFi transmission, additional care may be needed when U-TD LTEis deployed on the SCC.

Since U-TD LTE may be initiated on an SCC with the desire to causeminimal or no impact to WiFi, the HeNB may need to know the WiFioperational parameters beforehand to appropriately transmit U-TD LTEsubframes. The HeNB, with the help of a UE's measurements of theexisting WiFi transmissions, may initiate the transmission of U-TD LTEframes on the SCC. Further details on the UE's feedback of WiFi-specificmeasurements are provided below. The U-TD LTE subframes may consist ofadditional special subframes (in addition to S subframes), as describedbelow.

Some of the WiFi bands have power level restrictions, such as the U-NIILow band, whose power is limited to 50 mW. Such power restrictions arenot of concern for implementing LTE in the unlicensed band, since LTEHeNBs meet the transmit power constraints required for unlicensedoperation. The maximum transmit power for LTE HeNBs is less than 20 dBmfor Type 1 Home Base Stations and less than 13 dBm for Type 2 Home BaseStations. These power levels are consistent with the unlicensed bandrequirements provided above.

The following assumptions may be made in the discussion hereinafter. TheHeNB is assumed to be CA-capable and capable of operating over thelicensed and unlicensed frequency bands. 20/40 MHz channelization isassumed to be consistent with IEEE 802.11. U-TD LTE is assumed to beenabled for use only as an SCC. The U-TD LTE unlicensed band secondarycomponent carrier (U-SCC) is assumed to support only the U-Plane, andthe C-Plane is assumed to be present only in the PCC. The U-SCC isassumed to be configured primarily for downlink operation, to supplementa primary LTE licensed band component carrier (PCC), while the uplink issupported only by the PCC. The U-TD LTE frame structure on the PCC andthe U-SCC are assumed to be subframe and radio frame synchronized tominimize the impact to the current LTE standards. However, the UL-DLconfiguration may be different on the U-SCC and the PCC.

The unlicensed band may constitute a secondary component carrier in theLTE transmission configuration, as illustrated with an example in FIG.5. The SCC 510 may be added when traffic demands cannot be met by thePCC 520. The LTE bands identified for TDD operation are generally invarious ranges between about 1850 MHz and about 2620 MHz. The PCC may beassumed to be located in one of these bands. The U-SCC may be located inthe U-NII band at 5 GHz (e.g., 5725-5825 MHz in the US, a band that isused by wireless ISPs mostly in rural areas) or some other suitableunlicensed band. For example, a 20 MHz PCC at 2.5 GHz may be coupledwith a 20 MHz U-SCC at 5 GHz.

Since a UE may already be camping on an LTE femtocell licensed band PCC,there may be no need for cell search, association, and authenticationprocedures to be performed to activate the unlicensed band SCC. Instead,on initial association of a UE with the HeNB, a U-TD LTE capable HeNBmay transmit a query inquiring about the UE's U-TD LTE capability. Thisquery may be transmitted on the PCC to a UE that is in the region of theHeNB. A U-TD LTE capable UE may respond affirmatively to this query. TheHeNB may then update the UE's capability database for future use.

In an embodiment, the TD LTE PCC is leveraged to support the U-SCC.Several supporting functions for the U-SCC may be performed via the PCC.More specifically, device capability for U-TD LTE may be informed viathe PCC. Also, the carrier frequency and system parameters of the U-SCCmay be sent on system information broadcast on the PCC. Some of thesystem parameters, when changed, may be sent in dedicated radio resourcecontrol (RRC) signaling over the SCC. In addition, available channelsand a power limit may be signaled via the PCC, and synchronization maybe informed via the PCC. Also, the C-Plane may be exclusively with thePCC. Further, the U-SCC may not be used as a standalone LTE carrier.That is, UEs cannot attach to or access the LTE network through the SCCon the unlicensed band.

The bulk of the transmission, particularly the MAC signaling, may becarried by the PCC, thus leaving the U-SCC to be implemented in a simplemanner for carrying LTE data packets and higher layer control signals onthe downlink only. This approach simplifies U-TD LTE design since therestricted use of U-TD LTE only in the form of an SCC may require thedesign to cover only the support for user data while all the physicalcontrol signaling is performed on the PCC.

Protocol stack considerations will now be discussed. In particular, theMAC and physical layer features will now be considered. The physicallayer of U-TD LTE is OFDMA-based and has 20 MHz channelization. Otherchannelization options are also available and may be suitable for use inthe unlicensed band. Two scenarios were illustrated in FIG. 2 for theuse of U-TD LTE. In one case, RAT-b was shown as the sole user on anunlicensed channel, in the context of two RATs operating on differentunlicensed carriers at the same time. In another case, the channel wasshared between RAT-a and RAT-c. The same physical layer frame format asused in licensed TD LTE may be employed with some modifications tosupport U-TD LTE operation in both cases.

The beacon that is transmitted in an 802.11 context provides the timingsynchronization for the stations attached to the AP. In the context ofTD LTE, there is already a physical layer timing synchronization signalbeing transmitted, and this may be utilized for timing synchronizationon the U-TD LTE channel. An embodiment that provides a designenhancement in the case of coexistence with WiFi will now be provided.

Illustrations of U-SCC coexisting with 802.11 on the same 20 MHz channelare shown in FIGS. 6a, 6b , 7, and 8. The TD LTE UL-DL configurationsdefined in 3GPP TS 36.211 are used in the following examples. FIGS. 6a,6b , 7, and 8 illustrate the coexistence of U-TD LTE with UL-DLconfiguration #3 with 802.11. The other UL-DL configurations can also beused to adjust the bandwidth usage between the two RATs. The 802.11beacon interval is assumed to be at about 100 ms in the followingdescription, and this corresponds to the 802.11 superframe duration.However, any other beacon interval may be equally applicable. The lengthof an LTE TDD radio frame is 10 ms, so there can be multiple LTE radioframes within an 802.11 superframe.

In an embodiment, when the UE measurement feedback indicates that theWiFi beacon transmission occurs concurrently with a downlink subframetransmission on the PCC, as shown in FIG. 6a , the following proceduremay be used to configure the transmission during the U-TD LTE subframeon the U-SCC. The procedure takes into account an 802.11 coexistencesubframe (the LTE X subframe), a special blocking DL subframe Y, amodified U-TD LTE special subframe S, and a UL null subframe. In oneembodiment, these subframes can be scheduled by the higher layers.

Regarding the 802.11 coexistence subframe (the LTE X subframe), asillustrated in FIG. 6a , the LTE HeNB configures the DL subframe, e.g.the sixth subframe in a radio frame, of every tenth radio frame (e.g.,radio frames n, n+10, . . . etc.) whose transmission is concurrent witha WiFi beacon transmission as a special subframe X. For LTE to coexistwith 802.11 transmissions on the same channel (20 MHz), the beacon frametransmission from the 802.11 AP should not be interfered with by the LTEtransmission. For this reason, the LTE HeNB allots X subframes duringthe 802.11 beacon transmission. The X subframe is introduced only whenthere is an 802.11 beacon transmission in progress. Therefore, there maybe a need for the LTE HeNB to be aware of the beacon transmissionopportunities from the 802.11 AP. During the X subframe, there is notransmission during τ_(Beacon) ms, and during the rest of the subframe ablocking signal is transmitted. It may be assumed that the duration of aWiFi beacon transmission is less than 1 ms. τ_(Beacon) may include theduration of the beacon transmission from the 802.11 AP and any othertime variation expected by the beacon transmission from the AP. Itshould be noted that the AP may delay the beacon transmission based onthe ongoing packet transmission. The blocking signal is transmittedduring the rest of the X subframe to avoid 802.11 device transmission inthe immediately following subframes, which are dedicated to the U-TD LTEDL transmission. The beacon's TBTT parameter may be read by the HeNB inorder to schedule the X subframe at the appropriate time.

Regarding the blocking DL subframe, the sixth subframe in the otherradio frames is configured as a blocking subframe Y. A blocking signalis transmitted during the initial τ_(B1) ms of the subframe. The rest ofthe subframe is used for data transmission. (This is under theassumption that τ_(B1) is less than or equal to 3/15 ms). That is,subframes will occur at positions within subsequent LTE radio framesthat correspond to the position within a previous LTE radio frame wherea coexistence subframe was transmitted. If the WiFi AP is not scheduledto transmit a beacon signal concurrently with such a subsequentsubframe, the LTE eNB transmits a blocking subframe Y. For example, inFIG. 6a , a coexistence subframe X is transmitted in the sixth subframeof radio frame #n. When the sixth subframe of radio frame n+9 occurs, nobeacon signal is scheduled to be transmitted by the WiFi AP. Therefore,the LTE eNB transmits a blocking subframe Y in the sixth subframe ofradio frame n+9. More details on the blocking signal format are providedbelow.

The modified U-TD LTE special subframe S may optionally be taken intoaccount in this procedure. That is, the TD LTE specific special subframeS may need some changes for coexistence. As depicted in FIG. 6a , theHeNB may transmit a blocking signal during the guard period (GP). Thismay be required to avoid any 802.11 device-initiated transmissionsduring the UpPTS. It should be noted that UEs may transmit RACHpreambles or SRS transmissions during this period. In addition, it maybe preferable to have a guard time at the end of the UpPTS, during whichthe LTE HeNB does not transmit on the DL. This guard time, indicated asτ_(G) in FIG. 6a should be slightly greater than the DIFS. The settingof these parameters may depend on the various S subframe configurationsdefined in 3GPP TS 36.211. Alternatively, as depicted in FIG. 6b , theUpPTS may be set to one OFDM symbol and no SRS transmission may bescheduled on the U-SCC. In this configuration, no changes may berequired to the special subframe S for the coexistence.

Regarding the UL null subframe, the U-TD LTE configuration may require aminimum of one UL subframe during each U-TD LTE frame. Since U-TD LTE isdesigned only for the DL, the UL subframe is replaced with a nullsubframe.

The blocking symbol duration shown in FIG. 6a implies that there is noU-TD LTE data transmission during the period identified by the blockingsymbol.

FIG. 7 illustrates a coexistence scenario when the WiFi beacontransmission is concurrent with the UL subframe of the TD LTE subframeboundary on the PCC. In this case, the coexistence subframe X may not berequired.

FIG. 8 illustrates a coexistence scenario when the WiFi beacontransmission is concurrent with the special subframe S of the U-SCC. Inthis case, the special subframe S may require some changes to allow theWiFi beacon transmission. Based on which part of the S subframe the WiFibeacon aligns with, DwPTS, GP, and UpPTS may be configured as blank.That is, if the WiFi beacon aligns with the DwPTS, no DL transmissionmay be scheduled during the DwPTS. In this scenario, the primarysynchronization signal (PSS) and the broadcast channel (BCH) are nottransmitted on the U-SCC.

If the WiFi beacon aligns with the UpPTS, the UpPTS can be configuredsuch that no LTE UL transmission is expected during the UpPTS. That is,the system information block (SIB) can be set such that UEs do nottransmit the SRS or the RACH. Therefore, a WiFi AP can transmit thebeacon during this time. However, this is only done during every 10thradio frame. If the WiFi beacon is not concurrent with the transmissionof the fourth OFDM symbol of the special subframe, the PSS can betransmitted as usual.

Another alternative is to select the WiFi carrier whose beacontransmission does not collide with the S subframe. Yet anotheralternative is to offset the subframes on the PCC and U-SCC if the WiFibeacon transmission collides with the S subframe.

The above discussion has assumed that the TBTT is a multiple of 10 ms,but the above procedures can be generalized for other cases. If the TBTTis not a multiple of 10 ms (i.e., one LTE radio frame), the beacontransmission may not always align with the same type of subframe, namelya downlink, uplink, or special subframe. In such cases, the LTE HeNB mayneed to schedule the special blocking transmissions as suggested inFIGS. 6a, 6b , 7, and 8 based on specific radio frames. For example, ifthe TBTT is 105 ms instead of 100 ms, and if a beacon is known to bealigned with subframe #4 of radio frame n, then scheduling of blockingsymbols may be performed according to FIG. 6a during subframe #9 ofradio frame n+10. This scenario is depicted in FIG. 9.

In general, if a beacon occurs during the mth subframe of the nth radioframe, then the future subframes ┌ mod(n*10+m+lp, 10)+0.5┐ in radioframes └(n*10+m+lp)/10┘ are configured as suggested in FIGS. 6a, 6b , 7,and 8 based on whether the subframe is assigned to a DL or UL or Specialsubframe transmission, respectively. Here p indicates the TBTT expressedin ms. l indicates the lth beacon transmission. └x┘ and ┌x┐ indicate thelargest integer not greater than x and smallest integer not less than x,respectively. Therefore, the HeNB should be aware of the TBTT and alsoone specific beacon transmission to start the synchronization process.These parameters may be obtained via UE feedback, or the HeNB maymeasure these parameters.

As described above, the channel resources should be blocked by the HeNBsuch that all the WiFi devices sense a busy medium while U-TD LTE isusing the channel. For effective blocking of the channel, the transmitpower of the LTE transmissions should meet a certain criterion. It maybe assumed that the WiFi device detects a busy medium by measuring theaverage received signal power. It should be noted that these methods maybe at least partially dependent on the implementation.

The transmission power over the blocking symbols and downlinktransmission may be adjusted such that the busy medium detectioncriterion at the WiFi device is satisfied. For example, a WiFi devicemay sense the transmission medium over the carrier frequency f_(U) anddecide to transmit a packet if the medium is determined to be vacant fora DIFS time period. The channel sensing may include measuring thereceived power over 20 MHz. The power measurement P may be averaged overa finite duration of time.(P _(i)>η)

The threshold η is a design parameter and P_(i) is the received powermeasured at the WiFi device-i. P_(i) is compared to the threshold η.Therefore, the transmit power on the unlicensed carrier at the HeNB maybe adjusted such that the DL transmission on U-SCC effectively blocks oravoids accidental WiFi packet transmission. Therefore, the HeNB mayensure that the data transmissions towards the UEs that are operating onU-SCC are spread over the available resources with sufficient transmitpower to effectively block the WiFi transmissions.

It can be seen from FIGS. 6a, 6b , 7, and 8 that the WiFi beacontransmission may occur during an LTE subframe dedicated for downlink,uplink, or special transmission. Based on the scenario, differentcoexistence techniques as disclosed above may be enabled by the RRC/MACof the HeNB. A specific coexistence technique may be enabled with thehelp of UE feedback. If the UE is capable of receiving 802.11 and LTEtransmissions, the UE may be instructed to monitor the 802.11transmissions and feed back the measurement report to the HeNB. The UEmay be specifically asked to monitor the beacon transmissions from the802.11 AP.

As illustrated in FIG. 10, the HeNB may have, for example, three WiFiAPs within its coverage area, and the WiFi APs may be naturallyoperating over different carriers to avoid interference. The HeNB mayrequest measurement feedback from an active set of UEs on the unlicensedcarriers. Based on the measurement feedback, the HeNB may select f_UL1as the carrier frequency for the SCC.

Parameters that the UE may be requested to measure and feed back mayinclude but are not necessarily limited to WiFi beacon timing, themaximum time variation of the beacon, path loss, WiFi beacon lengthparameters, WiFi system load, and the maximum size of the WiFi MACpayload.

Since the 802.11 beacon transmission may vary within a time window, theWiFi beacon timing reception measurements with respect to an LTEsubframe reception may be averaged over multiple transmission windowsand reported back to the HeNB. That is,

$\overset{\_}{\tau} = {\frac{1}{N}{\sum\limits_{i = 0}^{N - 1}\tau_{i}}}$where τ_(i) is the ith measurement made with respect to the n_(i)thsubframe of m_(i)th radio frame. The average number of subframes betweentwo beacon transmissions can be measured as follows:

$\overset{\_}{n} = {{\frac{1}{N}{\sum\limits_{i = 0}^{N - 1}\left( {n_{i + 1} - n_{i}} \right)}} + {10*\left( {m_{i + 1} - m_{i}} \right)}}$where τ is measured as the time difference of arrival between thereception of the beacon and the nearest subframe edge. The subframe andradio frame number with respect to which these measurements are made mayalso be indicated in the report. FIG. 11 illustrates WiFi beacon timingrelative to the LTE subframe.

With regard to the maximum time variation of the beacon, the WiFi beacontransmission may vary based on an ongoing WiFi packet transmission froma WiFi device. The maximum time variation can be measured and may bereported back to the HeNB as

$\tau_{M} = {\max\limits_{i}\left\{ \tau_{i} \right\}}$

The UE may also measure and report the path loss L with respect to theWiFi AP, the average length and the maximum length of the WiFi beacon,the maximum MAC payload size as set by the WiFi AP, and an indication ofthe WiFi system load. The WiFi system load might be determined by, forexample, monitoring the WiFi medium busy periods.

Concepts related to the MAC layer will now be considered. FIG. 12illustrates a portion of the MAC layer, and elements 1210 represent anew functionality disclosed herein where a downlink SCH (DL-SCH) is on acomponent carrier unlicensed band.

Since there is one MAC per user, and link adaptation is performed perCC, the LTE CA design may make it convenient to incorporate theunlicensed band DL. The MAC DL SCH is supported on the U-SCC. The U-TDLTE scheme uses centralized scheduling similar to the TD LTE scheme. TheHeNB scheduler treats the U-TD LTE channel as an additional resource andschedules selected transmissions on the U-TD LTE channel when thechannel is available for use by LTE. With a centralized schedulingfunction controlling the allocation of spectrum to the UEs, there may beno need for the DCF and collision avoidance schemes used in IEEE 802.11.The MAC payload data unit (MPDU) size is not constrained as in IEEE802.11. The start of the U-TD LTE transmission may not require anyspecial medium access protocols in the case of coexistence in frequencywhen there are no other transmissions in the chosen band. Forcoexistence in time, there may be a need to ensure that the TD LTE frameis protected to avoid packet loss from initial collisions with ongoingtransmissions. UEs operating on the U-SCC may monitor the DL packet lossor any other channel quality indicator and send that information back tothe HeNB. Based on that information, the HeNB may decide to transmitsome of the DL packets via the PCC.

In these embodiments, the need for carrier sensing and collisionavoidance does not arise for interference from other U-TD LTE users inthe same band, particularly because the transmissions are primarilydownlink and managed by the scheduler. The design of U-TD LTE to operatein coexistence with WiFi on the same carrier is addressed elsewhereherein. Likewise, DCF is not needed because the transmissions aremanaged by the scheduler. Fairness of use to UEs in U-TD LTE can bemanaged by the scheduler. Fairness of use to other coexistingtechnologies is addressed elsewhere herein.

In an embodiment, the MAC frame format is the same as in TD LTE.However, it may be important to allow other RATs to access the spectrumwhile operating in coexistence mode. Instead of placing a minimum on theMPDU size, some of the subframes in the frame may be intentionally leftblank to allow other non U-TD LTE unlicensed spectrum users access tothe channel. However, the medium may need to be reclaimed in advance ofthe scheduled LTE transmission. This may be dealt with at the MAC layerby scheduling a blocking symbol in the physical layer. The blockingsymbol duration τ_(B1) ms may act as a buffer zone to capture thechannel for U-TD LTE transmission. When there is no WiFi or othertransmission detected (i.e., the channel is fully available for U-TDLTE), this special subframe may be employed for initial capture of thechannel. Once the channel is captured, the likelihood of WiFiinterference is decreased, since WiFi relies on CSMA/CA and will avoidtransmission as long as the channel is in use. Based on the scenariosdefined in FIGS. 6a through 8, the MAC layer may initiate the blockingsymbol transmission as needed.

The downlink data packets transmitted on U-SCC may be acknowledged onPCC UL subframes. In general, all the DL/UL control signaling to supportthe downlink transmission may be transmitted on the PCC. In addition,the LTE higher layers for both PCC and U-SCC may be maintained as is,since the actual air interface used for supporting an application orservice is transparent to the higher layers.

In addition to the above protocol stack considerations, conceptsregarding initiating the U-SCC, activating the U-SCC, and bandwidthsharing between WiFi and U-TD LTE will now be considered. As mentionedabove, the UEs may be assumed to already be on a PCC that is licensed TDLTE. When there is demand for more DL resources, the LTE HeNB mayinstruct the RRC_ACTIVE UEs that can also detect 802.11 to search for802.11 beacon transmissions over an unlicensed band in their vicinity.The channel search procedure may take into account information providedby the network about other eNBs in the vicinity using the unlicensedchannels.

The UEs may be requested to do specific measurements, such as theaverage power of the beacon received over the carrier frequencies withinthe unlicensed band, the average traffic load as observed by the UEs,and the approximate time difference of arrival between the 802.11 beaconand the LTE subframes transmitted over the PCC. Alternatively, the HeNBmay be equipped with means to scan and select the best channel.

Based on the UE measurement feedback, a carrier with the lowest beaconreceive power and lowest traffic load may be selected as a potentialU-SCC. The HeNB may notify the LTE network of the unlicensed channelthat is in use to prevent other HeNBs in the vicinity from selecting thesame channel.

The HeNB may communicate to a UE, in the signaling channel on the PCC,that the SCC is being set up in the unlicensed band for downlinkoperation. In addition, the HeNB may send the UE the transmit signalpower for the unlicensed channel for the UE's uplink transmissions ofcontrol messages such as an acknowledgement/negative acknowledgement(ACK/NACK). The HeNB may start transmitting the U-TD LTE frames afterappropriate synchronization of the transmissions over the U-SCC and thePCC.

FIG. 13 depicts an embodiment of a UE feedback initiation procedure toenable an SCC in the unlicensed band. At block 1310, an LTE eNB attemptsto detect a demand for bandwidth. If a demand for bandwidth is detected,then at block 1320, the eNB requests one or more UEs to scan the 802.11channels in the vicinity and report back the measurements. At block1330, a UE initiates measurements and reports back to the eNB.Information reported to the eNB may include the received power of thebeacon, a measure of traffic load (for example, by monitoring the powerfor some time), and an approximate measure of the time difference ofarrival between the 802.11 beacon and an OFDM symbol/subframe/radioframe on the LTE PCC. The UE may also obtain some of the 802.11 specifictimers, such as DIFS, and report that information back to the eNB. Atblock 1340, the eNB picks the channel with the lowest received beaconpower and/or the channel with less traffic. At block 1350, the eNBstarts transmitting the downlink synchronization/broadcast channels onthe selected channel. The eNB may also disable transmission on thedownlink subframe concurrent with the beacon transmission and enable the“blocking” transmission on some subframes to avoid interference from802.11a communication.

With regard to activating the U-SCC, the UE may optionally be asked toreport measurements about the 802.11 APs within the vicinity, eitherduring RRC connection establishment or immediately after RRC connectionestablishment and before or during S1 path establishment. Based on thefeedback, an appropriate SCC that is already configured as a U-SCC maybe activated by sending a MAC control element to the UE on the PCC.Subsequently, any Carrier Aggregation (CA)-capable UE attached to thenetwork for the first time may be assigned DL resources on the U-SCC.

This procedure is illustrated in FIG. 14. At event 1402, an RRCconnection establishment procedure occurs between a UE and a PCell. Atevent 1404, the PCell sends a measurement request to the UE requestingfrom the UE the WiFi-specific parameters mentioned above, such as WiFibeacon timing and the time variation of the beacon. Event 1404 may beactivated if there is a scarcity of DL and/or UL bandwidth and there areUEs in the system that are capable of operating in U-TD-LTE mode. Atevent 1406, the UE sends a measurement response to the PCell. At event1408, an S1 setup procedure occurs between the PCell and a mobilitymanagement entity (MME). At event 1410, a UE context setup requestoccurs between the PCell and the MME. At event 1412, an AS securityactivation and RRC connection reconfiguration procedure occurs betweenthe UE and the PCell. At event 1414, the UE context setup procedurebetween the PCell and the MME is complete. At event 1416, data is sentfrom the UE to the PCell to a serving gateway to a PDN gateway. At event1418, a measurement response is sent from the PCell to the UE. At event1420, the bearers are updated. At event 1422, a measurement response issent from the UE to the PCell. At event 1424, RRC connectionreconfiguration occurs with configuration of the SCells. At event 1426,the SCells are activated. At event 1428, data is sent from the PDNgateway to the serving gateway to the SCell. At event 1430, data is sentfrom the SCell to the UE. At event 1432, data is sent from the PDNgateway to the serving gateway to the PCell to the UE. Although two eNBsare shown in FIG. 14, one for the licensed band and one for theunlicensed band, only one eNB may be present.

With regard to bandwidth sharing between WiFi and U-TD LTE, Table 1below shows the resource sharing on an unlicensed channel between 802.11and U-TD LTE for the available UL-DL subframe configurations. The tableis limited to a UL-DL switching periodicity of 10 ms. A similar tablecan be created for a 5 ms periodicity, but for a 5 ms periodicity, thebandwidth used for coexistence signaling may be increased. New TD LTEUL-DL configurations can be defined to extend the bandwidth sharing. Itshould be noted that the special subframe Y within the TD-LTE subframestructure uses 10% of the available time-bandwidth resources.

TABLE 1 Percentage bandwidth TD LTE Percentage Percentage available forUplink- bandwidth bandwidth coexistence signaling Downlink availableavailable (not including the Configuration for 802.11 for TD LTE specialsubframe) 3 30 ~50 10 4 20 ~60 10 5 10 ~70 10

The overall coexistence procedure with respect to HeNB operation isdepicted in FIG. 15. As shown, a HeNB operating in U-TD LTE with apreconfigured UL-DL configuration continuously monitors the Quality ofService (QoS) of each service flow with respect to the promised QoS. Ifit is determined that extra bandwidth will improve the QoS with respectto the active UEs and also for the incoming UEs, the HeNB may try tocapture a vacant carrier within a licensed or unlicensed band.

The HeNB may try to find UEs that are capable of coexisting with WiFi onthe same carrier. If there are no UEs with this capability, the HeNB mayinitiate a search for carrier frequencies with the same or otherlicensed bands. It may be assumed that priority is given to find acarrier in an unlicensed band. The procedure can be modified toprioritize the licensed band, based on the configuration of the HeNB.

If there are many UEs that are WiFi-coexistence-capable, then the HeNBmay initiate a UE measurement request for an empty WiFi carrier. Basedon the measurement feedback, the HeNB may claim an empty or unused WiFicarrier, and Procedure C may then be followed. If an empty or unusedcarrier is not found, Procedure A may then be followed. The UEs may befurther asked to send specific WiFi measurements as specified above toevaluate the possibility of sharing the bandwidth in time with WiFi. Ifthere are no UEs that are WiFi-capable, a licensed SCC may be employed,as in Procedure B. Procedures A, B and C are described in detail below.

More specifically, at block 1510 in FIG. 15, a TD-LTE is operating onlicensed component carriers with UL-DL configuration-j. At block 1515,the downlink is monitored for load and user QoS. The uplink mayoptionally be monitored as well. At block 1520, it is determined whetherthere is demand for more downlink and/or uplink bandwidth. If there isno such demand, the procedure returns to block 1510. If there is demand,then at block 1525, the UEs that are capable of coexisting on the samecarrier with WiFi on unlicensed bands are identified. At block 1530, itis determined whether such UEs have been found. If such UEs have notbeen found, then at block 1535, Procedure B, which will be described inmore detail below, is initiated. If such UEs have been found, then atblock 1540, a measurement request is sent to the UEs. The measurementrequest may specify a specific unlicensed band and measurement object.At block 1545, the measurement feedback is collected from the UEs. Atblock 1550, it is determined whether one or more empty channels havebeen found. If no empty channels have been found, then at block 1555,Procedure A, which will be described in more detail below, is initiated.If one or more empty channels have been found, then at block 1560,Procedure C, which will be described in more detail below, is initiated.

FIG. 16 illustrates an embodiment of Procedure A from FIG. 15, that is,a procedure for enabling U-SCC when there is an active WiFi transmissionwith available bandwidth to share. Based on the measurement feedbackreceived from the UEs, the HeNB may rank the detected CCs in order ofpreference. For example, the ranking may be done according to thefollowing procedure.

The rank, R_(i) of the ith CC is determined as follows:R _(i)=α(1−L _(i))+β*S _(i) +γ*f _(i) +ζ*N _(i)where α, β, γ and ζ are scaling factors that may be implementationdependent. L_(i) is the WiFi system load. S_(i) is the expected LTEspectral efficiency (SPE) if CC-i is selected as the U-SCC. This iscalculated based on the transmit power restrictions as specified by thespectrum regulations. f_(i) is a measure of how much control over thebandwidth sharing is possible with the allowed UL-DL configurations.This can change if the LTE configurations are changed. N_(i) is thenumber of attached UEs which are capable of operating in CC-i. Thisparameter may also include an operator-settable preference for specificunlicensed bands over the others.

f_(i) may also include the maximum WiFi MAC payload. If the maximum MACpayload is smaller, the collision of WiFi packets with the LTEtransmission can be kept low and the waste of bandwidth can be reduced.

The HeNB may select a CC with the highest rank and inform aself-organizing network (SON) entity or a network server, such as a HeNBgateway, about the selection. It may be assumed that the network serveror SON entity manages the usage of the secondary carriers across thefemto area. The U-SCC confirmation procedure will be further describedwith regard to FIG. 19. If the server positively responds to the HeNB,the HeNB may enable the secondary carrier according to the proceduresdescribed above. Further, the HeNB may continuously monitor the currentLTE usage on the U-SCC and may reconfigure the DL-UL configuration.

More specifically, at block 1610 in FIG. 16, a request is made forcoexistence specific measurements over WiFi channels. At block 1615, thecomponent carriers are ordered according to the following rank (highestrank first): R=α*(1−L)+β*S+γ*f+ζ*N. At block 1620, the CC with thehighest rank is picked. At block 1625, a confirmation procedure with aSON occurs. At block 1630, the new rule is sent to the radio admissioncontroller as a result of the confirmation procedure with the SON. Atblock 1635, the new SCC is enabled and the power constraints are setaccording to the emission restrictions. At block 1640, it is determinedwhether the WiFi beacon collides with the S frame. If the WiFi beacondoes collide with the S frame, then at block 1645, the primarysynchronization signal (PSS), secondary synchronization signal (SSS),and master information block (MIB) on the SCC are disabled (nottransmitted on the SCC). If the WiFi beacon does not collide with the Sframe, block 1645 is bypassed, and at block 1650, the current andexpected LTE load on the PCC and the SCC and the transmit power andresource scheduling requirements for WiFi are continuously monitored. Atblock 1655, it is determined whether more or less LTE resources arerequired. If not, the procedure returns to block 1650. If so, then atblock 1660, the UL-DL configuration on the SCC is changed and theappropriate signaling is sent to the UEs operating over the SCC. Atblock 1665, it is determined whether SCC resources are required. If so,the procedure returns to block 1650. If not, then at block 1670, the SCCis disabled.

FIG. 17 illustrates an embodiment of Procedure B from FIG. 15, that is,a procedure to search for an available CC within a licensed band if theHeNB does not find UEs that are coexistence capable. This figuredescribes the current mode of operation for the introduction of SCCs.More specifically, at block 1710 in FIG. 17, a search is performed for avacant component carrier within the licensed bands. At block 1715, it isdetermined whether vacant CCs have been found. If so, then at block1720, a CC is selected over which most of the attached UEs are capableof operating. If not, then at block 1725, the UEs are selectivelydropped or the user QoS is gracefully degraded. At block 1730, it isdetermined whether a CC has been found. If not, the procedure returns toblock 1725. If so, then at block 1735, a confirmation procedure with aSON occurs. At block 1740, the new SCC is enabled. At block 1745, thecurrent and expected LTE load on the PCC and the SCC and the transmitpower and resource scheduling requirements for WiFi are continuouslymonitored. At block 1750, it is determined whether SCC resources arerequired. If so, the procedure returns to block 1745. If not, then atblock 1755, the SCC is disabled.

FIG. 18 depicts an embodiment of Procedure C from FIG. 15, that is, aprocedure to enable U-SCC on an unused unlicensed channel. At block 1810in FIG. 18, a search is performed for a vacant component carrier withinthe unlicensed bands. At block 1815, a CC is selected over which most ofthe attached UEs are capable of operating and the best spectralefficiency (SPE). At block 1820, it is determined whether such a CC hasbeen found. If not, then at block 1825, the UEs are selectively droppedor the user QoS is gracefully degraded. If so, then at block 1830, aconfirmation procedure with a SON occurs. At block 1835, the new SCC isenabled with the transmit power restrictions. At block 1840, the currentand expected LTE load on the PCC and the SCC and the transmit power andresource scheduling requirements for WiFi are continuously monitored. Atblock 1845, it is determined whether SCC resources are required. If so,the procedure returns to block 1840. If not, then at block 1850, the SCCis disabled.

The carrier claiming procedure illustrated in FIG. 19 may apply to theprocedures of FIGS. 16-18. The procedure of FIG. 19 may avoid situationswhere two HeNBs claim the same CC as the U-SCC and thereby causeinterference to each other. More specifically, at block 1910, a “channelclaim request” with a preference is sent. At block 1915, the response isreceived. At block 1920, it is determined whether the response ispositive. If the response is positive, then at block 1925, the new SCCis enabled and the power constraints are set according to the emissionrestrictions. At block 1930, a “channel claim ACK” is sent to the SON.If the response is not positive at block 1920, the procedure moves toblock 1935, where a “channel non-claim ACK” is sent to the SON. At block1940, the CC with the next highest rank is picked. The procedure thenreturns to block 1910.

The embodiments disclosed herein provide for the introduction of anunlicensed TD LTE secondary component carrier for use in a LTE-A carrieraggregation scenario. The embodiments enable the use of an enhanced LTETDD frame structure that allows coexistence with WiFi or otherunlicensed transmissions. The disclosed U-TD LTE frame structure isdesigned to adapt to allow the operation of other unlicensed users inthe band and thus manage interference in the band. Other novel elementsinclude a procedure for selection of an unlicensed channel for use as aU-SCC and for operating in a coexistence mode.

The above may be implemented by a network element. A simplified networkelement is shown with regard to FIG. 20. In FIG. 20, network element3110 includes a processor 3120 and a communications subsystem 3130,where the processor 3120 and communications subsystem 3130 cooperate toperform the methods described above.

Further, the above may be implemented by a UE. An example of a UE isdescribed below with regard to FIG. 21. UE 3200 may comprise a two-waywireless communication device having voice and data communicationcapabilities. In some embodiments, voice communication capabilities areoptional. The UE 3200 generally has the capability to communicate withother computer systems on the Internet. Depending on the exactfunctionality provided, the UE 3200 may be referred to as a datamessaging device, a two-way pager, a wireless e-mail device, a cellulartelephone with data messaging capabilities, a wireless Internetappliance, a wireless device, a smart phone, a mobile device, or a datacommunication device, as examples.

Where the UE 3200 is enabled for two-way communication, it mayincorporate a communication subsystem 3211, including a receiver 3212and a transmitter 3214, as well as associated components such as one ormore antenna elements 3216 and 3218, local oscillators (LOs) 3213, and aprocessing module such as a digital signal processor (DSP) 3220. Theparticular design of the communication subsystem 3211 may be dependentupon the communication network in which the UE 3200 is intended tooperate.

Network access requirements may also vary depending upon the type ofnetwork 3219. In some networks, network access is associated with asubscriber or user of the UE 3200. The UE 3200 may require a removableuser identity module (RUIM) or a subscriber identity module (SIM) cardin order to operate on a network. The SIM/RUIM interface 3244 istypically similar to a card slot into which a SIM/RUIM card may beinserted. The SIM/RUIM card may have memory and may hold many keyconfigurations 3251 and other information 3253, such as identificationand subscriber-related information.

When required network registration or activation procedures have beencompleted, the UE 3200 may send and receive communication signals overthe network 3219. As illustrated, the network 3219 may consist ofmultiple base stations communicating with the UE 3200.

Signals received by antenna 3216 through communication network 3219 areinput to receiver 3212, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection, and the like. Analog to digital (A/D) conversion of areceived signal allows more complex communication functions, such asdemodulation and decoding to be performed in the DSP 3220. In a similarmanner, signals to be transmitted are processed, including modulationand encoding for example, by DSP 3220 and are input to transmitter 3214for digital to analog (D/A) conversion, frequency up conversion,filtering, amplification, and transmission over the communicationnetwork 3219 via antenna 3218. DSP 3220 not only processes communicationsignals but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 3212 andtransmitter 3214 may be adaptively controlled through automatic gaincontrol algorithms implemented in DSP 3220.

The UE 3200 generally includes a processor 3238 which controls theoverall operation of the device. Communication functions, including dataand voice communications, are performed through communication subsystem3211. Processor 3238 also interacts with further device subsystems suchas the display 3222, flash memory 3224, random access memory (RAM) 3226,auxiliary input/output (I/O) subsystems 3228, serial port 3230, one ormore keyboards or keypads 3232, speaker 3234, microphone 3236, othercommunication subsystem 3240 such as a short-range communicationssubsystem, and any other device subsystems generally designated as 3242.Serial port 3230 may include a USB port or other port currently known ordeveloped in the future.

Some of the illustrated subsystems perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 3232 and display3222, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions, such as a calculator or tasklist.

Operating system software used by the processor 3238 may be stored in apersistent store such as flash memory 3224, which may instead be aread-only memory (ROM) or similar storage element (not shown). Theoperating system, specific device applications, or parts thereof, may betemporarily loaded into a volatile memory such as RAM 3226. Receivedcommunication signals may also be stored in RAM 3226.

As shown, flash memory 3224 may be segregated into different areas forboth computer programs 3258 and program data storage 3250, 3252, 3254and 3256. These different storage types indicate that each program mayallocate a portion of flash memory 3224 for their own data storagerequirements. Processor 3238, in addition to its operating systemfunctions, may enable execution of software applications on the UE 3200.A predetermined set of applications that control basic operations,including at least data and voice communication applications forexample, may typically be installed on the UE 3200 during manufacturing.Other applications may be installed subsequently or dynamically.

Applications and software may be stored on any computer-readable storagemedium. The computer-readable storage medium may be tangible or in atransitory/non-transitory medium such as optical (e.g., CD, DVD, etc.),magnetic (e.g., tape), or other memory currently known or developed inthe future.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE 3200 such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. One or morememory stores may be available on the UE 3200 to facilitate storage ofPIM data items. Such a PIM application may have the ability to send andreceive data items via the wireless network 3219. Further applicationsmay also be loaded onto the UE 3200 through the network 3219, anauxiliary I/O subsystem 3228, serial port 3230, short-rangecommunications subsystem 3240, or any other suitable subsystem 3242, andinstalled by a user in the RAM 3226 or a non-volatile store (not shown)for execution by the processor 3238. Such flexibility in applicationinstallation may increase the functionality of the UE 3200 and mayprovide enhanced on-device functions, communication-related functions,or both. For example, secure communication applications may enableelectronic commerce functions and other such financial transactions tobe performed using the UE 3200.

In a data communication mode, a received signal such as a text messageor web page download may be processed by the communication subsystem3211 and input to the processor 3238, which may further process thereceived signal for output to the display 3222, or alternatively to anauxiliary I/O device 3228.

A user of the UE 3200 may also compose data items, such as emailmessages for example, using the keyboard 3232, which may be a completealphanumeric keyboard or telephone-type keypad, among others, inconjunction with the display 3222 and possibly an auxiliary I/O device3228. Such composed items may then be transmitted over a communicationnetwork through the communication subsystem 3211.

For voice communications, overall operation of the UE 3200 is similar,except that received signals may typically be output to a speaker 3234and signals for transmission may be generated by a microphone 3236.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on the UE 3200. Althoughvoice or audio signal output may be accomplished primarily through thespeaker 3234, display 3222 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call-related information, for example.

Serial port 3230 may be implemented in a personal digital assistant(PDA)-type device for which synchronization with a user's desktopcomputer (not shown) may be desirable, but such a port is an optionaldevice component. Such a port 3230 may enable a user to set preferencesthrough an external device or software application and may extend thecapabilities of the UE 3200 by providing for information or softwaredownloads to the UE 3200 other than through a wireless communicationnetwork. The alternate download path may, for example, be used to loadan encryption key onto the UE 3200 through a direct and thus reliableand trusted connection to thereby enable secure device communication.Serial port 3230 may further be used to connect the device to a computerto act as a modem.

Other communications subsystems 3240, such as a short-rangecommunications subsystem, are further optional components which mayprovide for communication between the UE 3200 and different systems ordevices, which need not necessarily be similar devices. For example, thesubsystem 3240 may include an infrared device and associated circuitsand components or a Bluetooth™ communication module to provide forcommunication with similarly enabled systems and devices. Subsystem 3240may further include non-cellular communications such as WiFi, WiMAX,near field communication (NFC), and/or radio frequency identification(RFID). The other communications element 3240 may also be used tocommunicate with auxiliary devices such as tablet displays, keyboards orprojectors.

The UE and other components described above might include a processingcomponent that is capable of executing instructions related to theactions described above. FIG. 22 illustrates an example of a system 3300that includes a processing component 3310 suitable for implementing oneor more embodiments disclosed herein. In addition to the processor 3310(which may be referred to as a central processor unit or CPU), thesystem 3300 might include network connectivity devices 3320, randomaccess memory (RAM) 3330, read only memory (ROM) 3340, secondary storage3350, and input/output (I/O) devices 3360. These components mightcommunicate with one another via a bus 3370. In some cases, some ofthese components may not be present or may be combined in variouscombinations with one another or with other components not shown. Thesecomponents might be located in a single physical entity or in more thanone physical entity. Any actions described herein as being taken by theprocessor 3310 might be taken by the processor 3310 alone or by theprocessor 3310 in conjunction with one or more components shown or notshown in the drawing, such as a digital signal processor (DSP) 3380.Although the DSP 3380 is shown as a separate component, the DSP 3380might be incorporated into the processor 3310.

The processor 3310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 3320,RAM 3330, ROM 3340, or secondary storage 3350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 3310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 3310 may beimplemented as one or more CPU chips.

The network connectivity devices 3320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, universal mobile telecommunications system (UMTS) radiotransceiver devices, long term evolution (LTE) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 3320 may enable the processor 3310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 3310 might receiveinformation or to which the processor 3310 might output information. Thenetwork connectivity devices 3320 might also include one or moretransceiver components 3325 capable of transmitting and/or receivingdata wirelessly.

The RAM 3330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 3310. The ROM 3340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 3350. ROM 3340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 3330 and ROM 3340 istypically faster than to secondary storage 3350. The secondary storage3350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 3330 is not large enough to hold all workingdata. Secondary storage 3350 may be used to store programs that areloaded into RAM 3330 when such programs are selected for execution.

The I/O devices 3360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 3325 might be considered to be a component of the I/Odevices 3360 instead of or in addition to being a component of thenetwork connectivity devices 3320.

In an embodiment, a method is provided for communication in a wirelesstelecommunication system. The method comprises adaptively designating,by a network element following a frame-based communication protocol, foruse as a secondary component carrier in a carrier aggregation scheme, atleast a portion of radio resources on an unlicensed band.

In another embodiment, a network element following a frame-basedcommunication protocol is provided. The network element comprises aprocessor configured such that the network element adaptivelydesignates, for use as a secondary component carrier in a carrieraggregation scheme, at least a portion of radio resources on anunlicensed band.

In another embodiment, a UE is provided. The UE comprises a processorconfigured such that the UE receives at least a portion of radioresources on an unlicensed band, the at least a portion of radioresources on the unlicensed band having been adaptively designated by anetwork element following a frame-based communication protocol for useas a secondary component carrier in a carrier aggregation scheme.

In another embodiment, a method is provided for communication in awireless telecommunication system. The method comprises adaptivelyusing, by a network element following a frame-based communicationprotocol, at least a portion of radio resources not being used byanother network element following a contention-based communicationprotocol.

In another embodiment, a method is provided for communication in awireless telecommunication system. The method comprises adaptivelyusing, by a network element following a 3GPP LTE protocol, at least aportion of bandwidth that is not being used by a network elementfollowing a WiFi protocol based on an IEEE 802.11 standard, wherein theportion of radio resources is on an unlicensed band that is used as asecondary component carrier in a carrier aggregation scheme.

The following are incorporated herein by reference for all purposes:3GPP TS 36.211, 3GPP TS 25.105 and 3GPP TR 36.808.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method performed by a base station of awireless telecommunication system, the method comprising: detecting, bythe base station, a demand for wireless radio resources; requesting, bythe base station, a user equipment (UE) to perform a scan for wirelesschannels in response to detecting the demand, wherein requesting the UEto perform the scan for wireless channels comprises the base stationrequesting the UE to perform the scan in response to detecting anincrease in demand for wireless radio resources over a licensed band;receiving, by the base station in response to the requesting, ameasurement report from the UE; selecting, by the base station afterreceipt of the measurement report, a wireless channel based on feedbackinformation obtained from the measurement report, the feedbackinformation corresponding to wireless channels within a vicinity of theUE; and transmitting, by the base station after the selecting, at leastone of a synchronization channel and a broadcast channel via theselected wireless channel.
 2. The method of claim 1, further comprisingdetermining whether to offload traffic onto an unlicensed band inresponse to detecting the increase in demand for wireless radioresources over the licensed band, wherein requesting the UE to performthe scan for wireless channels comprises the base station requesting theUE to scan for 802.11 beacon transmissions over the unlicensed band inresponse to detecting the increase in demand for wireless radioresources over the licensed band.
 3. The method of claim 2, furthercomprising offloading traffic from the licensed band onto the unlicensedband upon the base station determining that traffic requirements cannotbe satisfied by a primary component carrier (PCC) operating over thelicensed band.
 4. The method of claim 3, wherein offloading traffic fromthe licensed band onto the unlicensed band comprises: enabling, by thebase station, a secondary component carrier (SCC) to operate over theunlicensed band; and directing downlink traffic from the base station tothe UE via the SCC while directing uplink communications from the UE tothe base station via the PCC.
 5. The method of claim 4, wherein enablingthe SCC to operate over the unlicensed band comprises the base stationtransmitting a media access control (MAC) control element to the UE viathe PCC.
 6. The method of claim 4, wherein directing downlink trafficfrom the base station to the UE via the SCC comprises transmitting asubframe to the UE over the unlicensed band such that transmission ofthe subframe does not interfere or substantially interfere with anexisting transmission over the unlicensed band between an access pointand a second UE.
 7. The method of claim 1, wherein the feedbackinformation from the UE includes at least one of: Wi-Fi beacontransmission parameters; path loss; traffic load of a Wi-Fi system; or amaximum medium access control (MAC) payload size set by a Wi-Fi accesspoint (AP).
 8. The method of claim 7, wherein the base station selectsthe wireless channel according to at least one of a lowest traffic loador a lowest received beacon power, the method further comprising:responsive to transmitting the at least one of the synchronizationchannel and the broadcast channel, directing downlink traffic from thebase station to the UE via the wireless channel and directing uplinktransmissions from the UE to the base station via a different channelthan the wireless channel.
 9. A base station, comprising: at least onememory device; and a processor configured to execute instructions storedon the at least one memory device such that when executed, cause thebase station to: detect a demand for wireless radio resources; request auser equipment (UE) to perform a scan for wireless channels in responseto detecting the demand, wherein requesting the UE to perform the scanfor wireless channels comprises the base station requesting the UE toperform the scan in response to detecting an increase in demand forwireless radio resources over a licensed band; receive, in response tothe request, a measurement report from the UE; select, after receipt ofthe measurement report, a wireless channel based on feedback informationobtained from the measurement report, the feedback informationcorresponding to wireless channels within a vicinity of the UE; andtransmit, after the selecting, at least one of a synchronization channeland a broadcast channel via the selected wireless channel.
 10. The basestation of claim 9, wherein the base station is configured to determinewhether to offload traffic onto an unlicensed band in response todetecting the increase in demand for wireless radio resources over thelicensed band, wherein requesting the UE to perform the scan forwireless channels comprises the base station requesting the UE to scanfor 802.11 beacon transmissions over the unlicensed band in response todetecting the increase in demand for wireless radio resources over thelicensed band.
 11. The base station of claim 10, wherein the basestation is further configured to offload traffic from the licensed bandonto the unlicensed band upon the base station determining that trafficrequirements cannot be satisfied by a primary component carrier (PCC)operating over the licensed band.
 12. The base station of claim 11,wherein offloading traffic from the licensed band onto the unlicensedband comprises the base station: enabling a secondary component carrier(SCC) to operate over the unlicensed band; and directing downlinktraffic from the base station to the UE via the SCC while directinguplink communications from the UE to the base station via the PCC. 13.The base station of claim 9, wherein the feedback information from theUE includes at least one of: Wi-Fi beacon transmission parameters; pathloss; traffic load of a Wi-Fi system; or a maximum medium access control(MAC) payload size set by a Wi-Fi access point (AP).
 14. The basestation of claim 13, wherein the base station selects the wirelesschannel according to at least one of a lowest traffic load or a lowestreceived beacon power.
 15. A non-transitory computer medium storinginstructions executable by a processor of a base station such that whenexecuted, cause the base station to perform a method, the methodcomprising: detecting, by the base station, a demand for wireless radioresources; requesting, by the base station, a user equipment (UE) toperform a scan for wireless channels in response to detecting thedemand, wherein requesting the UE to perform the scan for wirelesschannels comprises the base station requesting the UE to perform thescan in response to detecting an increase in demand for wireless radioresources over a licensed band; receiving, by the base station inresponse to the requesting, a measurement report from the UE; selecting,by the base station after receipt of the measurement report, a wirelesschannel based on feedback information obtained from the measurementreport, the feedback information corresponding to wireless channelswithin a vicinity of the UE; and transmitting, by the base station afterthe selecting, at least one of a synchronization channel and a broadcastchannel via the selected wireless channel.
 16. The non-transitorycomputer medium of claim 15, wherein the method further comprisesdetermining whether to offload traffic onto an unlicensed band inresponse to detecting the increase in demand for wireless radioresources over the licensed band, wherein requesting the UE to performthe scan for wireless channels comprises the base station requesting theUE to scan for 802.11 beacon transmissions over the unlicensed band inresponse to detecting the increase in demand for wireless radioresources over the licensed band.
 17. The non-transitory computer mediumof claim 16, wherein the method further comprises offloading trafficfrom the licensed band onto the unlicensed band upon the base stationdetermining that traffic requirements cannot be satisfied by a primarycomponent carrier (PCC) operating over the licensed band.
 18. Thenon-transitory computer medium of claim 17, wherein offloading trafficfrom the licensed band onto the unlicensed band comprises: enabling asecondary component carrier (SCC) to operate over the unlicensed band;and directing downlink traffic from the base station to the UE via theSCC while directing uplink communications from the UE to the basestation via the PCC.
 19. The non-transitory computer medium of claim 15,wherein the feedback information from the UE includes at least one of:Wi-Fi beacon transmission parameters; path loss; traffic load of a Wi-Fisystem; or a maximum medium access control (MAC) payload size set by aWi-Fi access point (AP).
 20. The non-transitory computer medium of claim19, wherein the base station selects the wireless channel according toat least one of a lowest traffic load or a lowest received beacon power.